I. Field
This concerns a method for rating the fire resistance of a building structure, further certification of the rating, and the rated structure. Involved is application to the structure or its component(s) of fire control agent(s).
II. Art
The fire protection industry has seen many changes over the recent centuries. From the bucket brigades of long ago to modern fire departments, from sprinkler systems to stringent fire codes, the fire protection industry is constantly evolving.
Fire retardants have been around for many, many decades. Their use has spanned just about every major industry. The commercial market has driven fire retardant technology over the last half century or so, but more and more attention is being placed on use of fire retardants in the residential setting. Each year more and more people die from fires in the home, often from employment of modern, petroleum-based materials for the construction and furnishing of the home. While old standard type fire retardants could be used freely in the commercial sector, the residential sector presents a much different problem.
Because commercial and residential structures are commonly constructed, furnished, and occupied differently, the old standard type fire retardants used in the commercial setting were not good for the home. The contents of such fire retardants were toxic, and decomposed wood; hence, they were not safe for adults, children, or pets. If a fire started, the very chemicals that kept the fire from spreading also yielded gases that were just as dangerous, if not more so, than the smoke the fire was producing.
About the mid-1990s, newer fire retardants were developed that effectively inhibited the start, growth, and spread of fire. In general, among other things, these newer fire retardants were non-toxic, non-carcinogenic, and environmentally friendly. Through further development, these newer fire retardants were also improved to form a protective barrier when they came in contact with heat or flame, and, in addition, when heated or exposed to flame, they did not produce harmful or toxic gases. Instead, they helped to suppress the production of other toxic fumes and smoke. Among the most effective of these improved fire retardants are those available from NO-BURN, Inc., Wadsworth, Ohio.
Such improved fire retardants can be employed in residences.
Fire, in general, is very complex. Certain things about it, however, are known. Fire behavior is the science of fire and the factors that affect its ignition, growth and spread. Combustion (burning) is the self-sustaining process of rapid oxidation of a fuel being reduced by an oxidizing agent along with the evolution of heat and light. Oxidation is the complex chemical reaction of materials, commonly organic in nature, with oxygen or other oxidizing agents, which forms more stable compounds. Rusting is an example of very slow oxidation, and an explosion is an example of very fast oxidation. Between the two extremes, a free-burning stage of fire is what is most commonly encountered. Fire is generally classified as rapid oxidation, and it burns in two modes: flaming and surface combustion. The flaming mode of combustion can be represented by a fire tetrahedron, with each of the four sides separately representing oxygen, heat, fuel, and an uninhibited chemical chain reaction. The surface or smoldering mode of combustion is represented by a fire triangle, with sides representing oxygen, heat, and fuel. Understanding the fire tetrahedron is important. To stop a flaming fire, one or more sides (components) of the fire tetrahedron must be removed. Many currently available products work to remove the fuel source and to prevent the chemical chain reaction from occurring, forming a protective layer. While protected objects typically are damaged by heat through pyrolysis, they will not sustain the combustion process. Such products are considered to be proactive fire protection measures.
When a fire, however, starts and burns, it continually undergoes changes in size, growth, speed and temperature. These changes are known as fire phases, of which three are commonly recognized: the incipient phase; the free-burning phase; and the smoldering phase. In the incipient phase, at which many daytime fires in buildings are found, the room air has plenty of oxygen, and the fire is producing water vapor, carbon dioxide, and small amounts of sulfur dioxide, carbon dioxide, and other gases. While the temperature of the flame itself may be above a thousand degrees F., the overall temperature in the room may have only risen a few degrees. Most all fires in residences start through the incipient phase. If a fire starts at night when people are asleep or an incipient phase fire goes unchecked for just a few minutes, the fire rapidly grows to the free-burning phase. During this phase, oxygen-rich air is drawn into the flame, and heat is carried to the uppermost parts of the room with the rise of fire gases. As the hotter air spreads out across the ceiling, any combustible materials in the upper level of the room such as pictures, curtains, valances and blinds ignite. These can fall to the floor, further spreading the fire. The air temperature in the room in the upper regions of the room can be exceedingly high in this part of the free-burning phase, often exceeding thirteen hundred degrees F. As fire of this phase continues to consume combustible materials lower and lower in the room, the fire can erupt in a flashover. Flashover is where all the combustible materials in a room ignite simultaneously from the intense radiating heat from the upper walls of the room. This explosion of flames pushes the fire well into other portions of the structure. For example, the fire may be now found inside the walls of the structure, and may find its way up into the attic, across which it can spread, and spread into the volumes between other walls, say, along wooden two-by-four studs, and so forth. If no fresh air is available, the oxygen content decreases until it falls below a level that would support flaming combustion, and the fire then enters the smoldering phase. During this phase, no flame is visible. The fuel and heat, however, are still at levels at which, if oxygen is reintroduced, the fire will re-ignite, sometimes forcefully in what is known as a backdraft.
Not all fires are the same. The classification of a fire is based on what is actually burning. Class A fires are those fires in which ordinary combustible materials such as wood, cloth, paper, rubber and plastics are burning. Many house fires are caused when ordinary combustible materials catch fire. Removing any component of the combustion tetrahedron or triangle will stop a Class A fire. Class B fires are those fires in which flammable liquids are burning. Examples would be greases, gasoline and other fuels or other flammable liquids. Class C fires are those fires in which energized electrical equipment is involved. If possible, the electrical source should be safely disconnected, and the fire treated as a Class A or Class B fire. Class D fires are those in which a combustible metal such as magnesium, sodium or titanium is on fire. Typically, special agents must be used to extinguish Class D fires.
It would be desirable to improve upon the known art. A notable desire would be to improve the art in a comprehensive manner. It would be most desirable to improve the art that concerns fire protection about building structures, especially residences.